Pete235 and I were talking about this the other day. It's hard to stay motivated when your primary objective was to be fit for your sport, and now you don't do the sport anymore.
Just jump back in to training! Listen carefully to your body, and if you think you are overdoing it, scale it back a bit. That's the nice thing about having a background in a sport, you know your body.
I personally enjoy the soreness that comes from knowing that I trained hard in the gym.
Let your soul be your guide on your ship of dreams.
Never, never, never quit.